Sterilization methods are used in a broad range of applications, and have used an equally broad range of sterilization agents. As used herein the term “sterilization” refers to the inactivation of all bio-contamination, especially on inanimate objects. The term “disinfectant” refers to the inactivation of organisms considered pathogenic.
Gaseous and vapor sterilization/decontamination systems rely on maintaining certain process parameters in order to achieve a target sterility or decontamination assurance level. For hydrogen peroxide vapor sterilization/decontamination systems, those parameters include the concentration of the hydrogen peroxide vapor, the degree of saturation, the temperature and pressure and the exposure time. By controlling these parameters, the desired sterility assurance levels can be successfully obtained while avoiding condensation of the hydrogen peroxide due to vapor saturation.
Because of the potential for degradation of the sterilant, monitoring the hydrogen peroxide concentration within a sterilization or decontamination chamber is important to ascertain whether sufficient sterilant concentration is maintained long enough to effect sterilization of objects within the chamber.
To insure the flow of hydrogen peroxide to the vaporizer, it has been known to use pressure switches to measure the static pressure head of the hydrogen peroxide solution in the injection lines to a vaporizer to insure there is sterilant in the injection lines. Some systems utilize a balance to measure the actual mass of the sterilant being injected into a vaporizer. In systems where pressure switches are used, the static head pressure may be reduced when a vacuum is created in the deactivation chamber. This vacuum may cause the pressure switch to generate a false “no sterilant” alarm. In cases where a balance is used to measure sterilant flow, there is no guarantee that the sterilant is actually making it to the vaporizer. Broken lines or disconnected tubing between the balance and the vaporizer can lead to false belief of sterilant in the decontamination chamber. Still further, any system, like the aforementioned pressure switches or balances, that precedes the vaporizer cannot detect or insure that the sterilant actually reaches the decontamination chamber.
It has also been known to detect the presence of vaporized hydrogen peroxide (VHP) in a chamber by means of chemical or biological indicators. Biological indicators, however, must be incubated for several days before knowing if sterilant is present, and chemical indicators generally provide a visual indication (typically by changing colors), thereby requiring operator intervention to abort a sterilization/decontamination cycle if the chemical indicators do not provide a positive indication of the presence of the sterilant. Another shortcoming of biological and chemical indicators is that they can only provide an indication of the presence of vaporized hydrogen peroxide (VHP), but cannot provide an indication of the amount of vaporized hydrogen peroxide (VHP) present.
It has been proposed to use infrared (IR) sensors to determine the actual vaporized hydrogen peroxide (VHP) concentration present. But IR sensors are expensive, delicate and bulky, making accurate vaporized hydrogen peroxide (VIP) measurements difficult. In this respect, it is desirable that measurements be made in real time as a sterilization process proceeds.
The present invention overcomes these and other problems, and provides a system for detecting concentrations of vapor hydrogen peroxide in a sterilization/deactivation chamber.